U.S. patent number 4,364,832 [Application Number 06/340,044] was granted by the patent office on 1982-12-21 for separating member in a separating tube for centrifugal separation.
Invention is credited to Uwe W. Ballies.
United States Patent |
4,364,832 |
Ballies |
December 21, 1982 |
Separating member in a separating tube for centrifugal
separation
Abstract
A separating tube (2) preferably made from a plastics material
for centrifugal separation of a liquid containing at least two
components and preferably blood is provided, in which an
asymmetrically shaped separating member (6) serves to separate the
two components. The separating member (6) has a specific gravity
between that of the two components to be separated. As a result of
the asymmetrical shape, the center of gravity (S) of separating
member (6) is eccentrically positioned with respect to axis (M) of
separating tube (2), so that the separating member (6) is rotated
or tilted during centrifuging. At least one gap (f) is formed
through which one of the two components reaches the top of
separating member (6). At the end of the centrifuging process, the
bouyancy of the heavier component rotates separating member (6)
back into its original position in which it seals off separating
tube (2). FIG. 4 is intended for publication with the summary.
Inventors: |
Ballies; Uwe W. (2300 Kiel,
DE) |
Family
ID: |
6122999 |
Appl.
No.: |
06/340,044 |
Filed: |
January 18, 1982 |
Foreign Application Priority Data
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|
|
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Jan 21, 1981 [DE] |
|
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3101733 |
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Current U.S.
Class: |
210/518; 494/16;
422/918 |
Current CPC
Class: |
B01L
3/50215 (20130101) |
Current International
Class: |
B01L
3/14 (20060101); B01D 021/26 () |
Field of
Search: |
;210/782,789,513,514,515,516,517,518,927 ;233/1R,1A,26 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Therkorn; Ernest G.
Attorney, Agent or Firm: Cushman, Darby & Cushman
Claims
I claim:
1. Separating member in a separating tube for the centrifugal
separation of a liquid containing at least two components, which
has a top surface and a bottom surface and is made from inelastic
material, particularly inelastic plastic material, whose specific
gravity is between that of the components to be separated and which
in the rest state seals the cross-section of the separating tube,
characterized in that the centre of gravity (S) of the separating
member (6-6'") is arranged eccentrically with respect to its
central axis (M) and that due to its shape, during centrifuging,
the separating member (6-6'") can only be tilted in the separating
tube (2) in such a way that a gap (f) is formed between the largest
circumference (D.sub.1) of the separating member (6-6'") and the
inner wall of the separating tube (2).
2. Separating tube according to claim 1, characterized in that the
separating member (6) is shaped like an asymmetrical frustum, whose
largest diameter D.sub.1 is twice as large as its smallest diameter
(D.sub.2), the two diameters D.sub.1 and D.sub.2 being connected by
a generatrix of the separating member (6) positioned vertically on
both the largest diameter D.sub.1 and the smallest diameter
D.sub.2.
3. Separating tube according to claim 1, characterized in that the
separating member (6") is in the shape of a cylindrical portion
with a circular top surface (7) under whose free end is provided a
separating wall (12) preventing an overturning of separating member
(6").
4. Separating tube according to claim 3, characterized in that the
underside (9) of the top surface (11) is inclined from its free end
to the bottom surface (5") of separating member (6").
5. Separating tube according to claim 1, characterized in that the
separating member (6'") is shaped like a cone with a rounded bottom
surface (5'").
6. Separating tube according to claim 5, characterized in that the
predetermined breaking point (16) is shaped into the rounded bottom
surface (5'").
7. Separating tube according to claim 1, characterized in that the
separating member (6, 6") has a conical top surface (7').
8. Separating tube according to any one of the claims 1 to 5 and 7,
characterized in that the separating member (6-6'") is shaped onto
a piston rod (15) by a predetermined breaking point (16).
9. Separating member according to claim 8, characterized in that
the predetermined breaking point (16) is located on the planar top
surface (7) of separating member (6) containing the largest
diameter D.sub.1.
10. Separating tube according to claim 8, characterized in that the
predetermined breaking point (16) is located at the tip of the
conical top surface (7', 7").
11. Separating tube according to one of the claims 1 to 5 and 7,
characterized in that the separating member (6-6'") has at least
one eccentrically arranged bouyancy chamber (10).
12. Separating tube according to claim 1, characterized in that the
separating member (6-6'") is made from polystyrene.
Description
The invention relates to a separating member in a separating tube
for the centrifugal separation of a liquid containing at least two
components, which has a top surface and a bottom surface and is
made from inelastic material, particularly inelastic plastic
material, whose specific gravity is between that of the components
to be separated and which in the rest state seals the cross-section
of the separating tube.
Such a separating tube is already known from DE-OS 2,711,336, in
which a substantially cylindrical polystyrene separating member is
placed in a plastic separating tube. During centrifuging, the
separating tube diameter is widened somewhat due to compression,
whereas the rigid plastic separating member does not change shape.
This leads to an annular clearance between the separating member
and the inner wall of the separating tube, so that under the
influence of the centrifugal force the separating member moves
towards the bottom of the separating tube. The lighter components
pass through the annular clearance into the space of the separating
member, which is deposited on the heavier component. At the end of
centrifuging, there is once again a close engagement between the
inner wall of the separating tube and the separating member leading
to the closure of the annular clearance, so that a complete
separation of the two components is achieved and maintained.
A disadvantage of the known separating tube is that it cannot be
made from a material which, during centrifuging, does not expand in
the radial direction, so that glass tubes cannot be used for this
purpose.
The problem of the present invention is to improve the known
separating tube in such a way that, during centrifuging, a gap is
still formed between the separating member and the separating tube
wall, if the latter is made from a material which does not
expand.
According to the invention, this problem is solved by a separating
tube of the aforementioned typed, which is characterized in that
the centre of gravity of the separating member is arranged
eccentrically with respect to its axis and that due to its shape,
during centrifuging, the separating member can only be tilted in
the separating tube in such a way that a gap is formed between the
largest circumference of the separating member and the inner wall
of the separating tube.
As a result, the separating member tilts during centrifuging in the
separating tube and consequently forms a gap through which the
lighter component can pass from the bottom to the top of the
separating member.
Preferably, the separating member is shaped like an asymmetrical
frustum, whose largest diameter D.sub.1 is twice as large as its
smallest diameter D.sub.2, the two diameters D.sub.1 and D.sub.2
being connected by a generatrix of the separating member positioned
vertically on both the largest diameter D.sub.1 and the smallest
diameter D.sub.2. In cross-section or in elevation, such a
separating member is trapezoidal. With respect to the axis of the
separating tube, the centre of gravity of the separating member is
positioned eccentrically, so that during centrifuging the
separating member is tilted in such a way that the centre of
gravity migrates towards the central axis M of the separating tube.
The separating member is in contact by two diametrically opposite
points with the inner wall of the separating tube and forms two
crescent-shaped gaps for the passage of the components to be
separated. Overturning of the separating member is prevented
through one point of the bottom surface being in contact with the
separating tube wall in one extreme or end position.
According to another embodiment of the invention, the separating
member is shaped like a cylindrical portion with a circular top
surface, which is perpendicular to the generatrix of the
cylindrical portion and seals the separating tube diameter in the
rest state. The circumference of the cylindrical portion is smaller
than a semi-circle, so that the separating member can tilt during
centrifuging.
The underside of the top surface is preferably bevelled towards the
bottom surface of the separating member, so that no air can remain
enclosed under the separating member.
To prevent an overturning of the separating member a separating
wall is provided on the underside of the free top surface having an
edge which, in the rest position of the separating member, is at an
angle to the separating tube wall. When the separating member is in
an end position, said separating wall edge comes into contact with
the separating tube wall and prevents a further tilting or rotary
movement.
According to a further embodiment of the invention, the separating
member is conical with a spherical shell-shaped bottom surface, the
height of the cone engaging on the spherical shell-shaped surface
being smaller than half the diameter of the separating tube. If,
during centrifuging, the cone points upwards, the centre of gravity
is above the largest diameter of the separating member and as a
result the latter has an unstable position, so that it will rotate
and bring the apex of the cone in a downwards direction.
According to a preferred embodiment of the invention, the
separating member is shaped by means of a predetermined breaking
point on a piston rod so that, prior to centrifuging, it can be
used in the manner of a syringe plunger. After raising the syringe,
the piston rod is stopped to which end, in the case of a conical
separating member, additionally two spaced tori are shaped onto the
inner wall of the separating tube in the vicinity of its upper end.
These tori form bearing blocks for stopping the piston rod.
According to another embodiment, said bearing block is formed by
the separating tube wall.
The tilting or rotary movement of the separating member is also
aided by the fact that, according to a preferred embodiment, at
least one bouyancy chamber is provided which, prior to
centrifuging, encloses air in the position of rest of the
separating member.
Preferably, the bouyancy chamber is arranged in an area
diametrically facing the centre of gravity, so that the bouyancy
force aids the action of the centrifugal force acting in the centre
of gravity during the rotation of the separating member.
The slope of the bouyancy chamber wall is chosen in such a way that
although air can be enclosed in the rest state, during centrifuging
it entirely passes out of the bouyancy chamber, so that after
centrifuging there is no air in the area of the separating layer
between the two components and which could have a disadvantageous
effect thereon.
Further advantageous developments of the invention can be gathered
from the subclaims and the following description of the
drawings:
The invention is described in greater detail hereinafter relative
to non-limitative embodiments and the attached drawings, wherein
show:
FIG. 1 a sectional view of an embodiment prior to centrifuging.
FIG. 2 a sectional view according to FIG. 1 during
centrifuging.
FIG. 3 a sectional view according to FIG. 1 after centrifuging.
FIG. 4 a sectional view according to FIG. 1 for representing the
movement sequence on passing from the rest position of FIG. 1 into
the end position according to FIG. 3.
FIG. 5 the position of the separating tube according to FIG. 1
prior to centrifuging.
FIG. 6 the position of the separating tube and separating member
during centrifuging.
FIG. 7 the position of the separating tube and separating member at
the end of centrifuging.
FIG. 8 a perspective view of the separating member according to
FIGS. 1 to 7 without a bouyancy chamber.
FIG. 9 a sectional view of the separating member of FIG. 8 shaped
onto a piston rod.
FIG. 10 a further construction of the separating member according
to FIGS. 1 to 9.
FIG. 11 a sectional view of the separating member according to FIG.
10 broken off from the piston rod.
FIG. 12 another construction of a separating member in perspective
view.
FIG. 13 a sectional view of the separating member according to FIG.
12.
FIG. 14 a sectional view of another construction of the separating
member shaped onto a piston rod.
FIG. 15 the separating member according to FIG. 14 broken off from
the piston rod after centrifuging.
FIG. 16 a perspective view of the separating member according to
FIGS. 14 and 15.
FIGS. 1 to 3 show a construction of a separating member 6 during
the individual phases of the centrifuging process. In the drawings,
a separating tube 2 is shown in the horizontal position, which is
frequently adopted during centrifuging. The separating tube 2 is,
for example, made from a plastics material or glass and is
initially sealed by a stopper 4. By means of a connecting member 8,
a separating member 6 in the form of an asymmetrical body is with
an eccentric centre of gravity S fitted to the underside of the
stopper 4. The two components or phases to be separated are
indicated by short lines or dots, the former indicating the liquid
phase and the latter a heavier, e.g. solid phase dispersed therein.
The connecting member 8 is, for example, an adhesive layer whose
bond with the separating member 6 is broken as a result of the
action of centrifugal force. The separating member 6 shown in FIGS.
1 to 9 has a circular top surface 7 and an also circular bottom
surface 5, which are in parallel planes. The circular top surface 7
has the same external diameter D.sub.1 as the internal diameter of
separating tube 2, whilst diameter D.sub.2 of the bottom surface 5
is half as large as the top surface diameter D.sub.1. The distant
between bottom surface 5 and top surface 7 corresponds to the
height of separating member 6 which, in cross-section, is shaped
like a right-angled trapezium. In the rest state according to FIG.
1 a generatrix of the separating member 6 is located on the wall of
the separating tube 2, whilst the diametrically facing generatrix
connecting top surface 7 and bottom surface 5 passes from the inner
wall of separating tube 2 to the separating tube axis M. Due to the
shaping of separating member 6 its centre of gravity S is not
located in the separating tube axis M, but is arranged
eccentrically with respect thereto by amount e.
The separating member shown in FIG. 1 also has in its half facing
the centre of gravity S, at least one bouyancy chamber 10, which
encloses air L in the state of rest according to FIG. 1.
FIG. 2 shows the state which occurs after the centrifugal force has
acted for a certain time, the separating member 6 having been
detached from connecting member 8 and a partial separation of the
two phases having taken place through gap f between separating
member 6 and the tube wall as a result of the tilting of the
separating member. This tilting or rotation of separating member 6
is brought about in that on the one hand the centrifugal force
acting in the centre of gravity S attempts to rotate the latter in
the separating tube axis M. The rotary movement is indicated by
arrow A. Simultaneously, a bouyancy force acting in the bouyancy
chamber 10 functions in the opposite direction to the action of the
centrifugal force, so that a pair of torques is formed, which aids
the rotary movement of separating member 6 in the direction of
arrow A. During tilting or rotating, the separating member 6 is
supported on the inner wall of separating tube 2 on two
diametrically facing points which, on the circumference of top
surface 7 are located in the normal plane passing through
separating tube axis M on the sectional or drawing plane.
During further centrifuging, the liquid phase moves past the
separating member 6, which slides in the direction of the tube
bottom and finally, according to FIG. 3, floats on the heavier
phase. As a result of the bouyancy on immersion in the heavier
phase, the separating member 6 is rotated back into the initial
position in which it seals off the diameter of separating tube 2.
The air L enclosed in bouyancy chamber 10 prior to centrifuging is
completely discharged during centrifuging, so that in the end
position according to FIG. 3, none of the restoring bouyancy force
acts against the heavier phase. In addition, no air is enclosed in
the bouyancy chamber 10, which would disadvantageously influence
the heavier phase.
Separating member 6 can be made from a random material,
particularly plastic. It can be solid, hollow or filled with
additional weights. Bouyancy chamber 10 can be open towards the
periphery of separating member 6. According to another
construction, the bouyancy chamber is enclosed and contains a
granular material as an additional bouyancy member. When separating
blood, preference is given to the use of a separating member made
from a glass-hard, light-weight plastics material, preferably
polystyrene, which has a specific gravity of .about.1.045, i.e. it
is lighter than the erythrocytre layer with a specific gravity of
.about.1.09 and somewhat heavier than the plasma or serum layer,
whose specific gravity is <1.04 to 1.045.
FIG. 4 illustrates the action and arrangement of bouyancy chamber
10 by means of five positions of the separating member 6 during
centrifuging which, for reasons of clarity, are shown one above the
other in a separating tube 2. In the drawing, a normal line N is
assumed to be placed on separating tube 2 and/or separating tube
axis M, with respect to which is given the angles of the chamber
wall slope .alpha..sub.I-V and the top surface slope
.beta..sub.I-V.
In the initial or rest state according to FIG. 4I, separating
member 6 is hung by means of connecting member 8 on stopper 4. Its
top surface 7 is parallel to the normal line N of separating tube
2, so that the top surface slope .beta..sub.I is 0.degree. with
respect to the normal line N. Bouyancy chamber 10 is filled with
air L.sub.I. In part, there is also liquid W.sub.I in bouyancy
chamber 10 and in fact the position of the liquid level is defined
by the right-hand upper edge of chamber 10 in FIG. 4I. The bouyancy
chamber 10 is shaped in such a way that during moulding it can be
removed from the mould in a sloping manner to the right. For this
purpose, the chamber opening must at least have the same diameter
as the rest of the chamber in order to permit the use of an unsplit
mould. In the case of a bouyancy chamber with a smaller chamber
opening then the internal diameter of the chamber it is necessary
to use a split mould in the production of the separating
member.
FIG. 4II shows the position of separating member 6 following the
start of centrifuging, a gap f.sub.II being formed by rotation in
the direction of arrow A.sub.II.
In FIG. 4II, this is a counterclockwise rotation. Part of the air
L.sub.II enclosed in bouyancy chamber 10 can now escape through gap
f.sub.II, whilst liquid W.sub.II flows into bouyancy chamber 10.
The chamber wall slope .alpha..sub.II is smaller than in FIG. II,
whereas the top surface slope .beta..sub.II has increased.
In FIG. 4III, separating member 6 has been rotated to such an
extent by pivoting in the direction of arrow A.sub.III that the
chamber wall slope has come into a negative area with respect to
the normal line N. The liquid W.sub.III subsequently flows into
bouyancy chamber 10 and thereby displaces all the air L.sub.III and
the bouyancy due to air L which has previously existed in the
right-hand of separating member 6 is discontinued. In this
position, the top surface slope .beta..sub.III is at a maximum,
whereas the chamber wall slope .alpha..sub.III has its greatest
negative value of e.g. 5 to 20 and preferably 10.degree..
In the case of further downward movement of separating member 6 in
separating tube 2 according to FIG. 4IV, a bouyancy force B caused
by the immersion in the heavier phase acts counter to the rotation
direction of arrow A.sub.III, so that separating member 6 rotates
back in the direction of arrow A.sub.IV and consequently the size
of gap f.sub.IV is reduced. The chamber wall slope .alpha..sub.IV
again passes into the positive range, i.e. below normal line N,
whilst the top surface slop .beta..sub.IV is reduced again.
In the end position according to FIG. 4V, the separating member 6
floats on the heavier phase and has again sealed separating tube 2.
Top surface 7 is again located parallel to normal line N, so that
the top surface slope is .beta..sub.V =0. The chamber wall slope
.alpha..sub.V has again reached its maximum value and we obtain
.alpha..sub.V =.alpha..sub.I. It is now completely free from air
and entirely filled with liquid W.sub.V, which constitutes the
heavier phase.
FIGS. 5 to 7 show the absolute position of separating tube 2 in a
centrifuge, the same parts once again being designated by the same
references.
FIG. 5 shows the hung-in separating tube 2 prior to centrifuging,
the centrifuge axis being designated C. The speed of the centrifuge
is V.sub.I =0.
FIG. 6 shows the separating tube 2 during centrifuging and at
rotational speeds V.sub.II-IV, corresponding to the separating
member positions II-IV in FIG. 4.
Finally, FIG. 7 shows the end position of separating tube 2
achieved at maximum centrifuging speed V.sub.V and which
corresponds to the separating member position in FIG. 4V.
FIG. 8 is a perspective view of separating member 6 clearly showing
top surface 7 with its diameter D.sub.1 and bottom surface 5 with
its diameter D.sub.2. A predetermined breaking point 6 is shaped in
the centre of the circular, planar top surface 7 by means of which
separating member 6 follows onto a piston rod 15 indicated in FIG.
9. The separating tube axis M passes through the centre of the top
surface 7 and consequently through the predetermined breaking point
16. The centre of the circular bottom surface 5 is displaced by
D.sub.1 /4 with respect to the centre of top surface 7, i.e. by
half the radius of the latter, so that in plan view bottom surface
5 extends from one edge of top surface 7 to the predetermined
breaking point 16 located in its centre. This leads to the shape,
apparent from FIG. 9, of a right-angled trapezium with a generatrix
parallel to the wall of separating tube 2. Separating member 6 can
also be used as a piston or plunger for the suction of blood and,
in the aforementioned manner, is shaped on a piston rod 15 by means
of a predetermined breaking point 16 in the manner indicated
hereinbefore. After drawing up blood into separating tube 2, whose
underside is provided for this purpose with a sealable cannula cone
18 not shown in FIG. 9 but clearly visible in FIG. 10, piston rod
15 is broken off by clockwise bending or breaking off, separating
member 6 being supported against the wall of separating tube 2.
In the case of separating member 6 of FIGS. 9 and 8, no bouyancy
chamber is provided, but it is obvious that the separating member
shaped onto a piston rod can also be equipped with a bouyancy
chamber according to FIGS. 1 to 7.
FIGS. 10 and 11 show a different construction of separating member
6' connected by means of a conical top surface 7' to piston rod 15.
The same parts are once again given the same references. A
predetermined breaking point 16 is once again provided at the tip
of the conical top surface 7'. Separating member 6' has at least
one bouyancy chamber 10, represented in part sectional form in FIG.
10. In FIG. 11, the bouyancy chamber 10 is indicated by a dot-dash
line. The separating tube according to FIG. 10 has on its bottom a
cannula cone 18 through which can be sucked the blood or the liquid
to be separated. After raising separating member 6', the piston rod
15 is broken off in the previously described manner and the top of
the separating tube 2 is sealed by its overlapping stopper 4'. The
cannula core 18 is also closed by a cover or cap, which is known
per se, but not shown for reasons of clarity.
FIG. 11 shows the broken-off separating member 6' in the initial
position, as well as the stopper 4' provided with a conical
depression corresponding to top surface 7'.
FIGS. 12 and 13 show a further construction of the separating
member, the same parts once again being indicated by the same
references. The modified separating member is designated 6" and has
a circular top surface 7, onto which follows a cylindrical portion
11. The circumference of the cylindrical portion 11 is shorter than
half a circumference, so that the greatest width of portion 11 is
smaller than the diameter of top surface 7 and consequently
separating tube 2. This makes it possible to tilt separating member
6" in separating tube 2 in a counterclockwise direction according
to FIG. 13.
FIG. 13 shows separating member 6" in section, it being clear that
the underside 9 of top surface 7 runs in an inclined manner from
the wall of separating tube 2 to the bottom surface 5" of
separating member 6" and with the top surface 7 forms an angle of
e.g. 5 to 20 and preferably 10.degree.. As a result, air trapped
under the top surface 7 can escape from the underside 9 of
separating member 6" on tilting the latter. Beneath free top
surface 7 is also provided a separating wall 12, whose lower edge
13 ends at a distance from the wall of separating tube 2 and
consequently prevents overturning of separating member 6" during
centrifuging. Thus, in elevation, separating member 6" has
approximately the outer contour of separating member 6 shown in
FIGS. 1 to 9. Once again, separating member 6" is shaped onto a
piston rod 15 by means of a predetermined breaking point 16 and can
be broken off therefrom by bending away the piston rod 15 after
drawing up the blood or the liquid to be separated. In FIG. 13,
breaking off takes place by moving piston rod 15 in a clockwise
direction, so that cylindrical portion 11 is supported on the wall
of separating tube 2 and forms a bearing block.
FIGS. 14 and 16 show a further embodiment of the invention with a
conical separating member 6'", whose tip is once again shaped by
means of a predetermined breakingpoint 16 on a piston rod 15 which
can be broken off. The same parts are once again given the same
references in these drawings. The conical separating member 6'"
therefore has a conical top surface 7'", whose largest external
diameter corresponds to the internal diameter of separating tube 2.
The conical top surface 8'" is followed by a domed bottom surface
5'", which in the represented embodiment is a spherical portion.
The largest diameter of spherical portion D.sub.1 is shown in
broken line form in FIG. 14 and corresponds to the internal
diameter of separating tube 2. The height of the top surface cone
from its base containing diameter D.sub.1 to the tip formed by the
predetermined breaking point 16 is somewhat less than half the
internal diameter D.sub.1 of the separating tube 2, so that after
breaking away from piston rod 15 during centrifuging, separating
member 6'" can completely revolve (cf FIG. 15). At least one
bouyancy chamber 10'" is also eccentrically arranged in the domed
bottom surface 5'", so that the centre of gravity S is once again
positioned eccentrically with respect to the separating tube axis
M. On drawing up the liquid to be separated, air can be enclosed in
bouyancy chamber 10' ", which aids an overturning of separating
member 6'" during centrifuging. FIG. 15 shows the overturned
separating member 6'" after breaking off and now the domed bottom
surface 5'" points upwards. As bouyancy chamber 10'" is also open
at the top, no air remains enclosed.
For breaking separating member 6'" off from piston rod 15, two tori
20, 21 are provided aththe upper end of separating tube 2 and are
spaced in such a way that they jam separating member 6'" on the
periphery. The outer torus 20 is larger in the radial direction of
separating tube 2, so that a removal of separating member 6'" from
tube 2 is considerably impeded. The inner torus 21 is somewhat
smaller, so that separating member 6'" can move over said torus
during pulling up. The two tori 20, 21 form a bearing block for
separating member 6'" for breaking off piston rod 15. Separating
member 6'" is thereby in the position indicated by dot-dash lines
in FIG. 14.
The inner and outer tori 20, 21 are, according to one embodiment,
positioned at one end of separating tube 2 and in this case a
stopper which externally engages round tube 2 is chosen. Such a
stopper is not shown for reasons of clarity, but it is obvious to
the Expert how such a stopper can be constructed. In another, not
shown embodiment, the two tori are spaced from the end of the
separating tube, so that the latter can be sealed by a stopper 4 or
4' represented in the preceding drawings.
FIG. 16 shows the conical separating member 6'" broken off from the
piston rod in a perspective view, it also being possible to see the
edge of bouyancy chamber 10'".
According to another, not shown embodiment, the separating member
according to FIGS. 14 to 16 is a solid member without a bouyancy
chamber, the revolving or tilting over of the separating member
taking place solely as a result of its unstable position after
breaking off from the piston rod.
According to another, not shown embodiment, the separating member
has roughly the shape according to FIG. 15, its top surface being
domed and its bottom surface conical. In this case, the domed top
surface is connected, prior to centrifuging, to a stopper by means
of a connecting member or is shaped by means of a predetermined
breaking point onto a piston rod. This separating member with a
domed top surface and conical bottom surface can once again have
one or more bouyancy chambers through which the previously enclosed
air can reliably escape during centrifuging. Appropriate
embodiments for the bouyancy chambers are described relative to
FIGS. 1 to 11.
It falls within the scope of the invention in the case of a
cross-sectionally quadrilateral separating tube to construct the
separating member in trapezoidal or triangular manner, so that once
again in the rest state the complete cross-section of the
separating tube is blocked, whereas during centrifuging there is
tilting of the separating member and consequently a gap is
formed.
* * * * *